Data compression method for use in wellbore and formation characterization

A method for acquiring and communicating image-producing data to a surface recording unit, comprising:

• measuring a value of a parameter of an earth formation penetrated by a wellbore at azimuthally spaced apart positions in the wellbore;
• determining an azimuthal orientation at which each of the values of the parameter is measured;
• determining a time at which each of the values of the parameter is measured;
• compressing the parameter values;
• encoding the compressed parameter values;
• and
• applying the encoded, compressed parameter values to a selected position in a telemetry format for transmission to the surface recording unit.

A method for determining rate of penetration of a drilling assembly in a wellbore, comprising:

• measuring, near the drilling assembly, a property of earth formations penetrated by the drilling assembly, the measuring performed by sensors at axially spaced apart locations;
• recording a time at which each of the measurements of the property are made;
• recording an azimuthal orientation of the sensors at the time each of the measurements is made;
• correlating azimuthally corresponding ones of the measurements made at a first one of the spaced apart locations to measurements made at a second one of the spaced apart locations;
• determining from the correlating when the first and the second one of the spaced apart location have made measurements in substantially the same earth formation;
• and
• calculating the rate of penetration from a difference in time between the measurements made in the substantially same earth formation at the first and second spaced apart locations and from a distance between the first and second spaced apart locations.

A method for determining dip of earth formations penetrated by a wellbore, comprising:

• moving an instrument forming part of a drilling assembly along the wellbore;
• measuring a property of the earth formations at azimuthally spaced apart positions using at least one sensor disposed at a selected axial position along the instrument, the measurements each including a record of an azimuthal orientation and a time at which the measurements are made;
• determining an axial position of the instrument along the wellbore with respect to the time records, so as to determine an axial position of each of the measurements of the formation property;
• determining an axial displacement of at least one layer boundary in the earth formations by correlating measurements made at selected, corresponding azimuthal orientations and at a plurality of the determined axial positions;
• and
• calculating the dip by combining the axial displacement with a measurement of the trajectory of the wellbore proximate the measurements of the formation property.

A method for determining dip of earth formations penetrated by a wellbore, comprising:

• moving an instrument along the wellbore;
• measuring a property of the earth formations at azimuthally spaced apart positions around the wellbore using at least one sensor disposed at a selected axial position along the instrument, the measurements each including a record of an azimuthal orientation and a time at which the measurements are made;
• correlating the measurements made by the at least one sensor to identify boundaries of layers in the formation measured by the at least one sensor, and determining a time difference between which the at least one sensor having measured corresponding ones of the layer boundaries;
• computing from this the difference an estimate of formation dip that would correspond to a fixed rate of movement of the instrument along the wellbore;
• transmitting to the earth's surface the estimate of formation dip;
• making a measurement at the earth's surface of the rate of movement of the instrument along the wellbore;
• using the measurement of movement made at the surface to convert the transmitted dip estimate into an estimate of the apparent dip of the corresponding layer boundaries;
• combining the estimate of apparent dip with a measurement of the trajectory of the wellbore proximate the measurements made of the formation property to provide an estimate of the dip of the formation layer boundaries.

A method for determining dip of earth formations penetrated by a wellbore, comprising:

• moving an instrument along the wellbore;
• measuring a property of the earth formations at azimuthally spaced apart positions using at least one sensor disposed at a selected axial position along the instrument, the measurements each including a record of an azimuthal orientation and a time at which the measurements are made;
• selecting an azimuthal reference which minimizes a sinusoidal component of an azimuthal Fourier transform of the data with respect to that reference;
• generating a discrete cosine transform of the Fourier-transformed data;
• identifying from the resulting 2D transformed data a corresponding apparent dip of the formation with respect to the wellbore;
• combining the corresponding apparent dip with a measurement of the trajectory of the wellbore proximate the measurements of the formation property to provide an estimate of the dip of the earth formation.